The present invention pertains to an arrangement in regenerative rotary heat exchangers, particularly air preheaters, for detecting and controlling clearance between a flange that projects radially outwards around the end surfaces of the rotor and axially in relation to movable sector plates of the rotor that mutually separate the two heat exchanging media.
Arrangements of this kind have been the subject of comprehensive development over a long period of time. The problem to be solved is that clearance detecting or sensing devices in particular are often exposed to troublesome ambient conditions, namely a corrosive and dirty atmosphere with considerable variations in pressure and temperature as the rotor rotates. This is because as the rotor sectors pass in towards and out from the edges of the sector plates the heat exchanging media will flow alternately around the sensors active between the sector plates and rotor flanges at alternately high and low pressures and exert a disturbing influence thereon. Despite efforts to compensate for disturbances, the effect of the ambient conditions renders sensing unreliable. As a result, developments have leaned towards more sophisticated solutions, such as slip shoes that include forward feed arrangements for compensating wear, and air cushion arrangements.